U.S. patent number 4,081,353 [Application Number 05/732,650] was granted by the patent office on 1978-03-28 for hydrodesulfurization with a specific alumina-supported catalyst.
This patent grant is currently assigned to Gulf Research & Development Company. Invention is credited to William L. Kehl, Angelo A. Montagna.
United States Patent |
4,081,353 |
Kehl , et al. |
March 28, 1978 |
**Please see images for:
( Certificate of Correction ) ** |
Hydrodesulfurization with a specific alumina-supported catalyst
Abstract
A process for the hydrodesulfurization of feedstocks under
comparatively low hydrogen partial pressures, i.e. less than about
1200 psig (8.27 MPa) in contact with a catalyst containing a
hydrogenation component supported on a particular carrier. The
carrier is a substantially silica-free alumina prepared by
calcining a material comprising a dried alumina (i) containing from
about 1.2 to about 2.6 moles of water of hydration per mole of
Al.sub.2 O.sub.3, (ii) having an (020) line width at 14.degree. (2
.theta.) at 3/4 maximum intensity of from about 2.0.degree. to
about 5.0.degree., and (iii) having an intensity ratio relative to
the intensity at 10.degree. (2 .theta.) of about 1.3 to about
5.0.
Inventors: |
Kehl; William L. (Pittsburgh,
PA), Montagna; Angelo A. (Monroeville, PA) |
Assignee: |
Gulf Research & Development
Company (Pittsburgh, PA)
|
Family
ID: |
24944428 |
Appl.
No.: |
05/732,650 |
Filed: |
October 15, 1976 |
Current U.S.
Class: |
208/216R;
208/217; 502/314 |
Current CPC
Class: |
B01J
21/04 (20130101); B01J 23/85 (20130101); C10G
45/10 (20130101); C10G 2300/107 (20130101) |
Current International
Class: |
B01J
21/00 (20060101); B01J 21/04 (20060101); B01J
23/85 (20060101); B01J 23/76 (20060101); C10G
45/08 (20060101); C10G 45/10 (20060101); C10G
45/02 (20060101); C10G 023/02 () |
Field of
Search: |
;208/216,217
;252/465,466J |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
3340180 |
September 1967 |
Beuther et al. |
3472759 |
October 1969 |
Masologites et al. |
3846285 |
November 1974 |
Beuther et al. |
3940330 |
February 1976 |
Beuther et al. |
3941683 |
March 1976 |
Beuther et al. |
|
Primary Examiner: Crasanakis; George
Claims
We claim:
1. A hydrodesulfurization process which comprises contacting a
sulfur-containing charge stock under mild conditions including a
temperature from about 600.degree. to about 1000.degree. F. and a
hydrogen partial pressure of from about 50 to about 1200 psig with
a hydrodesulfurization catalyst comprising from 2 to 25 weight
percent of a metalliferous hydrogenation component on a
substantially silica-free alumina hydrate which after drying and
before calcining comprises an alumina hydrate:
containing from about 1.2 to about 2.6 moles of water of hydration
per mole of Al.sub.2 O.sub.3 ;
and having an X-ray diffraction pattern wherein the width of the
(020) line at 14.degree. (2 .theta.) at three-fourths maximum
intensity is from about 2.0.degree. to about 2.0.degree.; and the
intensity ratio relative to the intensity at 10.degree. (2 .theta.)
is about 1.3 to about 5.0.
2. A process according to claim 1 wherein said charge stock is a
petroleum residual fraction.
3. A process according to claim 2 wherein the metalliferous
hydrogenation component comprises at least one metal selected from
the metals of Groups VI and VIII of the Periodic Table.
4. A process according to claim 3 wherein the hydrodesulfurization
catalyst contains in addition a promoting amount of a metal from
Group IVB.
5. A process according to claim 4 wherein the amount of the Group
IVB metal based on the metal in the zero valent state is from 1 to
10% by weight of the total catalyst.
6. A process according to claim 3 wherein the hydrogenation
component is a mixture of nickel, cobalt and molybdenum.
7. A process according to claim 1 wherein the alumina hydrate
support is formed by precipitating the alumina hydrate containing
from 1.2 to 2.6 moles of water of hydration per mole of Al.sub.2
O.sub.3 by the simultaneous addition of an aqueous solution of an
aluminum salt and an aqueous base at a pH between about 4.5 and
less than 7 until the addition of the aluminum salt is complete,
and thereafter increasing the pH in the precipitation medium by the
continued addition of the aqueous base to a pH in the range of
about 8 to 10.
8. A process according to claim 5 wherein the Group IVB metal is
titanium.
9. A process according to claim 5 wherein the sulfur-containing
charge stock is a residual petroleum fraction boiling substantially
above 950.degree. F. and containing the asphaltene content of the
crude.
10. A process according to claim 1 wherein said alumina has an
X-ray diffraction pattern substantially as shown on FIG. 1.
11. A process according to claim 1 wherein the alumina hydrate
support is formed by:
precipitating the alumina hydrate containing from 1.2 to 2.6 moles
of water of hydration per mole of Al.sub.2 O.sub.3 by the
simultaneous addition of an aqueous solution of an aluminum salt
and an aqueous base at a pH between about 4.5 and less than 7 until
the addition of the aluminum salt is complete;
increasing the pH in the precipitation medium by the continued
addition of the aqueous base to a pH in the range of about 8 to
10;
aging said precipitated alumina hydrate at said increased pH;
recovering the precipitate;
washing the precipitate;
and drying the precipitate to obtain said alumina hydrate:
containing from about 1.2 to about 2.6 moles of water of hydration
per mole of Al.sub.2 O.sub.3.
12. A process in accordance with claim 11 wherein said pH during
precipitation of said alumina hydrate is maintained constant at
about 5.5; the increased pH by the continued addition of the an
aqueous base is about 10; and the alumina hydrate is being aged for
about one hour before recovering the precipitate.
Description
This invention relates to a process for the hydrodesulfurization of
a feedstock employing comparatively low hydrogen partial pressures
and a catalyst comprising a hydrogenation component and a specific
carrier. More particularly this invention relates to a
hydrodesulfurization process in which the hydrogen partial pressure
is less than about 1200 psig (8.27 MPa), and wherein the catalyst
carrier is obtained by calcining a material consisting of a
particular form of a dried alumina.
DESCRIPTION OF STATE OF THE ART
The hydrodesulfurization of various feedstocks by contacting them
with hydrogen and a catalyst containing a hydrogenation component
on a support has previously been suggested in the prior art. Older
prior art in the area relating to hydrodesulfurization required the
use of elevated temperatures and pressures ranging up to 20,000
psig (138 MPa). More recent prior art, e.g. U.S. Pat. No. 3,846,285
issued to Beuther et al on Nov. 5, 1974, describes the
hydrodesulfurization of metals containing hydrocarbons at lower
temperatures and pressures having a catalyst having as the support
a material consisting of two different crystalline alumina
hydrates. The present invention relates to the discovery of a
further improved form of an alumina support for the catalyst to be
used in a process for the hydrodesulfurization of hydrocarbons.
The chemistry and crystallographic nature of alumina is quite
complex and has been under vigorous study for many years. Such a
study is justified by the quest for improved aluminas to serve as
supports for various catalytic purposes. For reasons which are not
fully understood, the nature of the alumina support is very
influential in the overall activity, selectivity and aging of
catalysts containing a metalliferous hydrogenation component when
used in a process for the desulfurization and/or demetallization of
hydrocarbon oils. Thus prior art patents such as U.S. Pat. No.
3,188,174 to Kehl et al and U.S. Pat. No. 3,222,273 to Kehl et al
teach the preparation of pseudoboehmite and also teach the
usefulness of the pseudoboehmite aluminas as precursors of supports
for catalysts destined for use in the hydrogenative desulfurization
of petroleum charge stocks. The more recent '285 patent to Beuther
et al mentioned above teaches, as noted, the use of a mixture of a
dihydrate and trihydrate of alumina as a catalyst support for
improved aging and regenerability characteristics when used for the
desulfurization of metals containing hydrocarbon charge stocks. The
dihydrate portion of the Beuther et al catalyst support has the
same chemical formula as the pseudoboehmite of Kehl et al.
As is well known, there is in reality a family of aluminas which
differ in chemical formula by the moles of water associated with
the Al.sub.2 O.sub.3. Thus alumina monohydrate is known as
"boehmite"; alumina trihydrate is variously known as "gibbsite" and
"bayerite". Kehl et al in the patents referred to above were the
first to recognize the existence of intermediate water content
aluminas referred to above as "pseudoboehmite", and taught
techniques for preparing the pseudoboehmites.
It has now been found that pseudoboehmites (Al.sub.2
O.sub.3.1.2-2.6 H.sub.2 O) can be prepared, which, although having
substantially the same moles of water per mole of alumina, differ
after drying and before calcining in their X-ray diffraction
patterns, especially in the 8.degree. to 16.degree. (2 .theta.)
region. For reasons which are not understood, it has been found
that catalysts supported on certain pseudoboehmites possess unusual
and unexpected activity for the desulfurization of hydrocarbons at
low temperatures and pressure.
BROAD STATEMENT OF INVENTION
In accordance with the invention, an improved hydrodesulfurization
process under comparatively low hydrogen partial pressure has been
discovered which comprises conducting the hydrodesulfurization
process in the presence of a catalyst comprising a metalliferous
hydrogenation component on a substantially silica-free alumina
which after drying and before calcining (i) contains from about 1.2
to about 2.6 moles of water of hydration per mole of Al.sub.2
O.sub.3, (ii) has an (0.20) line width at 14.degree. (2 .theta.) at
three-fourths maximum intensity of from about 2.0.degree. to about
5.0.degree., and (iii) has an intensity ratio relative to the
intensity at 10.degree. (2 .theta.) of about 1.3 to about 5.0.
FEEDSTOCKS
The feedstocks suitable for treatment in accordance with the
process of this invention include substantially any oil-like stock
boiling above about 400.degree. F. (204.degree. C.), such as, for
example, oils derived from shale, tar sands, or coal; substantially
full petroleum crudes boiling above 400.degree. F. (204.degree.
C.); topped crudes; reduced crudes; atmospheric or vacuum tower
bottoms; or any individual fraction. Thus the feedstock can be a
topped crude from which only the lowest boiling materials such as
naphtha boiling materials have been removed; or, more usually, it
can be a residual fraction boiling above about 950.degree. to
1000.degree. F. (510.degree. to 538.degree. C.). Similarly it can
be any of the intermediate distillate fractions such as furnace
oil, boiling from 400.degree. to about 650.degree. F. (204.degree.
to 343.degree. C.); or gas oil boiling from about 650.degree. to
about 950.degree. F. (343.degree. to 510.degree. C.). The feedstock
can also be a fraction or fractions separated on the basis of
solubility rather than boiling range, such as, for example, an
asphaltene or maltene fraction. It is preferred, however, in the
process of this invention to employ a feedstock which contains a
substantial quantity of residual components, asphaltic contaminants
and metalliferous components. Accordingly, the process of this
invention most advantageously can be used for the treatment of
residual petroleum fractions boiling substantially above
950.degree. F. (510.degree. C.) and containing the asphaltene
content of the crude.
The above described feedstocks, particularly the residual petroleum
based feedstocks, can contain up to about five to six weight
percent sulfur, although usually such feedstocks contain no more
than about four weight percent sulfur. Similarly the higher boiling
feedstocks contain substantial quantities of metalliferous
contaminants, for example, greater than about 50 ppm of metals,
particularly nickel and vanadium. Additionally the feedstocks
treated in accordance with the process of this invention can be
materials which have been previously subjected to a sulfur removal
operation, in which case the subject invention is effective to
provide a product having extremely low sulfur contents, for
example, less than about 0.5 percent by weight.
As used herein, the terms "residual", "residue" or "residual
components" are meant to describe the most difficultly vaporizable
portions of crude oils which normally cannot be distilled, in the
absence of a vacuum, without effecting decomposition of the stock.
Indicative of such residual components is a Conradson Carbon Number
usually greater than about 1. Such residual components can
typically be isolated as a separate fraction by vacuum
distillation, i.e. a vacuum tower bottoms, and generally boil above
about 950.degree. to 1000.degree. F. (510.degree. to 538.degree.
C.). The amount of residual components in a crude petroleum oil can
vary from substantially zero, as in a Pennsylvania crude, up to as
high as about 25% by volume for some Mideast crudes. It will be
understood, of course, that the concentration of residual
components in a fraction of a crude oil, such as a topped crude or
reduced crude, will be dependent upon the original concentration of
residual components in the full crude and the amount of lighter
materials removed. Generally, the feedstocks employed in the
process of this invention will contain at least 2% by volume
residual components and preferably at least about 5% by volume. It
will also be understood that the process of this invention provides
increased advantages when treating stocks containing increased
quantities of residual components.
OPERATING CONDITIONS
The operating conditions employed in the process of this invention
comprise a temperature in the range from about 600.degree. to about
1000.degree. F. (316.degree. to about 538.degree. C.) and
preferably from about 650.degree. to about 800.degree. F.
(343.degree. to about 427.degree. C.). The space velocity can be in
the range from about 0.1 to about 10.0, preferably less than about
5.0 and more preferably from about 0.1 to about 2.0 volumes of
charge stock per volume of catalyst per hour. The hydrogen feed
rate employed ranges from about 500 to about 10,000 standard cubic
feet per barrel of feedstock, preferably is in the range from about
1000 to 8000 standard cubic feet per barrel and more preferably is
in the range from about 2000 to about 6000 standard cubic feet per
barrel. The hydrogen partial pressure employed in the process of
this invention is in the range from about 50 to about 1200 psig
(about 0.34 to about 8.27 MPa), preferably less than about 1000
psig (6.9 MPa), and even more preferably less than about 800 psig
(5.5 MPa), with superior results being obtained with hydrogen
partial pressures as low as 500 or 400 psig (3.45 or 2.75 MPa).
Usually it is preferred to employ hydrogen partial pressures of at
least 200 psig (1.38 MPa). The total pressures employed in the
process of this invention do not greatly exceed the hydrogen
partial pressures, and the maximum total pressure is limited to a
maximum of about 1500 psig (10.3 MPa) and preferably a total
pressure of less than about 1000 psig (6.89 MPa).
CATALYST DESCRIPTION
The catalyst employed in the process of this invention comprises a
minor proportion of a metalliferous hydrogenation component, such
as one or more of the Group VI and Group VIII metals, their oxides
and sulfides, composited with a major amount of a particular
alumina. The total amount of the hydrogenation component is from 2
to 25 weight percent, preferably 4 to 15 weight percent, of the
catalyst based on the metal in the zero valent state. Preferably,
the hydrogenating component is one or more of the metals nickel,
cobalt, platinum, palladium, molybdenum and tungsten. The
particular alumina required in this invention must be substantially
silica-free. Thus, any silica incorporated cannot be more than
contaminant level, i.e., less than 1% by weight, and preferably
less than about 0.5% by weight. Accordingly, the alumina employed
in the process of this invention is not to be a so-called
silica-stabilized alumina, i.e. a material containing silica in an
amount from about 1 up to about 5% or 6% by weight. Additionally,
the catalyst can be promoted with from about 1% to about 10% by
weight, preferably at least about 2.5% of a Group IVB metal, i.e.
titanium, zirconium, and hafnium. It is preferred to employ
catalysts containing no more than about 8% by weight Group IVB
metal, and of these metals it is preferred to employ titanium and
zirconium, particularly titanium. It has also been found
advantageous that the Group IVB metal not be incorporated into the
carrier but rather be deposited on the carrier such as by
impregnation of the calcined carrier.
It has now been found in accordance with the invention that an
improved alumina can be prepared which results in even greater
activity for a hydrodesulfurization catalyst under mild conditions
than the alumina supports suggested in the prior art. The new
improved alumina after drying but prior to calcining contains from
about 1.2 to 2.6 moles of water of hydration per mole of alumina;
has an (020) line width at 14.degree. (2 .theta.) and at
three-fourths maximum intensity from about 2.0.degree. to
5.0.degree., preferably 3.degree. to 5.degree.; and has an
intensity ratio relative to the intensity at 10.degree. (2 .theta.)
of from 1.3 to 5.0, preferably 1.5 to 3.0. A typical x-ray
diffraction pattern for an alumina to be used as a support for the
catalysts of this invention is shown on FIG. 1. The line width and
intensity ratio in an X-ray diffraction pattern depend upon the
instrumentation conditions used. For purposes of the subject
invention, the following instrumentation conditions apply in
defining the line width and intensity ratio:
1. employ a Picker X-ray powder diffractometer using a copper
target X-ray diffraction tube operated at 35 kilovolts and 16
milliamperes tube filament current with 1.degree. slits and a
nickel filter to remove the copper K.sub..beta. radiation.
2. employ a detector consisting of a sealed gas-filled proportional
counter used in conjunction with a pulse amplitude discriminator;
and
3. the detector scanning rate should be 1.degree. (2 .theta.) per
minute, and the output signal should be recorded on a strip chart
recorder traveling at 15 inches (37.5 cm) per hour with a scale
factor set at 400 counts per second at full scale. Referring to
FIG. 1, it can be seen that the (020) line width at about
14.degree. (2 .theta.) and at three-fourths maximum intensity is
about 3.0.degree..
The (020) line width at about 14.degree. (2 .theta.) and
three-fourths maximum intensity is a rough measure of crystallite
size. As the line width increases, the crystallite size decreases.
Pseudoboehmites falling within the chemical formula Al.sub.2
O.sub.3. 1.2-2.6 H.sub.2 O can have greatly differing line widths
at about 14.degree. (2 .theta.), as is shown in FIGS. 2, 3 and 4
(designated pseudoboehmite Types I, II and III).
Referring to FIGS. 2, 3 and 4, the (020) line width at about
14.degree. (2 .theta.) and at three-fourths maximum intensity is
only measurable in FIG. 2 and is about 1.6.degree., while the line
width in FIGS. 3 and 4 is not measurable, indicating that the
crystallites are highly disordered along the b axis of the crystal
lattice.
FIG. 5 is the X-ray diffraction pattern for an alumina before
calcining which was prepared in accordance with Example 1 of U.S.
Pat. No. 3,846,285 referred to above. The alumina of FIG. 5 is
about 10% bayerite (trihydrate of alumina) and the remainder a
substantially uniform gelatinous material which is an alumina
dihydrate (pseudoboehmite). A comparison of FIGS. 1 and 5 readily
shows the considerable differences between the X-ray diffraction
patterns of these two aluminas. In FIG. 5 a line width at about
14.degree. (2 .theta.) cannot be measured, whereas the line width
at about 14.degree. (2 .theta.) and three-fourths maximum intensity
is about 3.degree. in FIG. 1, indicative of a larger crystallite
size for the FIG. 1 material. A similar conclusion results from a
comparison of FIG. 1 with FIGS. 3 and 4. On the other hand, FIG. 2
(which represents an alumina prepared in accordance with the
teachings of the '285 patent except no trihydrate is present) does
have a measurable line width at about 14.degree. (2 .theta. ) and
three-fourths maximum intensity, i.e. about 1.6.degree., which
indicates an even larger crystallite size. A further comparison of
FIG. 1 (the invention) and FIG. 2 (prior art), however, shows that
the peak at about 14.degree. (2 .theta.) bottoms out at a different
level at about 10.degree. (2 .theta.).
The "bottoming out" at a different level is the result of
differences in the nature and intensity of the continuous small
angle X-ray scattering. This continuous small angle scattering is
related to the existence of matter in the form of small particles,
or to heterogeneities in the scattering medium. When this
continuous small angle scattering extends to larger angles, it is
an indication of smaller particles (or smaller pores) or to greater
disorder in the lattice which results in increased heterogeneity.
This scattering is practically independent of the crystallinity of
the sample or short range order of the atoms comprising the
particles, and is not affected by deformations of the crystal
lattice. It depends only on the exterior form and dimensions of the
particles. On the other hand, a decrease in the crystallite size or
an increase in the disorder or deformation of the crystal lattice
results in an increase in the width of the X-ray diffraction lines
arising from the crystalline component of the sample. Thus by
observing both the nature of the small angle scattering and the
width of the lines of the X-ray diffraction pattern, it is possible
to assess the particle size of the sample including any amorphous
fraction that might be present and the crystallite size or the
deformation of the lattice of the crystalline component.
The "bottoming out" at a higher level in FIG. 1 than in FIG. 2 is
due to the combined effects of stronger small angle scattering at
larger angles and broader X-ray diffraction lines in FIG. 1. This
indicates that the alumina hydrate of FIG. 1 has smaller particles
and small crystallites (or greater deformation of the crystal
lattice) than the alumina hydrate of FIG. 2. The reasons for this
difference in particle size and crystallite size are not fully
understood, but experience has shown that whatever factors are
responsible for the differences in the development of larger
particles and crystals in these alumina hydrates will also affect
the structural transformation that occurs as a result of the
dehydration during the calcination step. This is illustrated, for
example, by the differences in the pore properties of the calcined
aluminas obtained as a result of calcining two alumina hydrates of
the type shown in FIG. 2 and FIG. 4. The alumina hydrate of FIG. 4
has smaller particles and smaller crystallites than the alumina
hydrate of FIG. 2. The pore characteristics of the two calcined
products are as follows:
______________________________________ Figure 2 Figure 4
______________________________________ Pore Vol (cc/g) 0.40 0.44
Avg. Pore Rad. (A) 29 25 Surface Area (m.sup.2 /g) 278 359 PSD (Vol
%) 100-300 A (rad.) 1.9 0.5 50-100 3.0 2.2 30-50 26.0 5.1 20-30
52.0 65.7 10-20 17.4 26.7
______________________________________
The calcined alumina derived from the FIG. 4 alumina hydrate has a
significantly larger surface area and a larger percentage of small
pores than the alumina derived from the FIG. 2 alumina hydrate.
Further comparison of the X-ray diffraction patterns of the alumina
hydrates of FIG. 1 and FIG. 2 shows that the lines in FIG. 1 are
not only broader but also are somewhat weaker than those in FIG. 2.
This is shown by the relative intensity of the line centered at
38.4.degree. (2 .theta.) in the two patterns. In FIG. 2 this line
has an intensity of 142 arbitrary units, as measured by the area
under the peak, whereas in FIG. 1 this line has an intensity of
only 120 units. This, coupled with the significantly higher
intensity of small angle scattering at angles out to 9.degree. (2
.theta.) in FIG. 1, indicates that an amorphous or highly
disordered component is present in the alumina hydrate of FIG. 1
which is not present, at least to the same extent, in the hydrate
of FIG. 2.
In the '285 patent (Beuther et al) the distinctive properties of
the activated alumina were attributed to a mixture of crystalline
phases (trihydrate and pseudoboehmite) in the precursor alumina
hydrates. In the present case, an apparently analogous result is
obtained from a mixture of the pseudoboehmite phase and an
amorphous or highly disordered phase in the precursor alumina
hydrate.
Whether an X-ray diffraction pattern similar to FIG. 1 represents
(i) a certain "disorder" in a small crystallite precursor
pseudoboehmite alumina, (ii) a mixture of phases, or (iii) some
other phenomenon, it has been discovered, in accordance with the
invention, that an alumina which before calcining has (i) from
about 1.2 to about 2.6 moles of water per mole of alumina and (ii)
an X-ray diffraction pattern similar to FIG. 1 is an unusually and
unexpectedly active support for hydrogenation catalysts to be used
for the desulfurization of feedstocks at mild conditions. Thus the
alumina precursors of this invention require not only a large (020)
line width (2.degree. to 5.degree.) at three-fourths maximum
intensity at about 14.degree. (2 .theta.) but also require a
"bottoming out" factor. To measure the "bottoming out" factor, an
"intensity ratio" was developed which is a ratio of the maximum
intensity (height) of the (020) line to the minimum point of the
background intensity at about 10.degree. (2 .theta.), measured, of
course, from the base line. The improved alumina supports for the
catalyst of this invention were found to have unusually low
intensity ratios, indicating a particular combination of disorder
in the alumina hydrate structure and small particles which, for
reasons not understood, results after calcining in an unusually
active support for catalysts for the hydrodesulfurization of
hydrocarbons. Referring to FIG. 1, the intensity ratio is the
maximum intensity (about 48) divided by the minimum point of the
background intensity at about 10.degree. (2 .theta.) (about 24), or
about 2.0. Suitable intensity ratios are from about 1.3 to 5.0. The
intensity ratio for the alumina in FIG. 2 (prior art) is about 10,
while intensity ratios are not measurable for the alumina
precursors represented by FIGS. 3, 4 and 5.
Many techniques for the preparation of alumina hydrates are well
known to those having ordinary skill in the alumina preparation
art, including several techniques for the preparation of the
crystalline alumina hydrates containing from 1.2 to 2.6 moles of
water of hydration per mole of Al.sub.2 O.sub.3, i.e. an "alumina
dihydrate" or "pseudoboehmite" alumina. U.S. Pat. No. 3,846,285
referred to above, for example, describes several general methods
of preparation in Columns 4 and 5, and working Example 1 of the
'285 patent details the preparation of the alumina shown in FIG. 5.
Any method of preparation which provides an alumina precursor
having the above-described X-ray diffraction pattern
characteristics in addition to 1.2 to 2.6 moles of water per mole
of alumina is satisfactory. One suitable method is to add a small
amount of an aluminum salt such as aluminum chloride to water and
then simultaneously add streams of aqueous aluminum chloride and
ammonium hydroxide so as to maintain a pH between about 4.5 and
less than 7, preferably less than 6.5. If a pH of less than about
4.5 is employed, a thick gel forms which is difficult to break, and
thus the minimum pH should be some pH above this thick gel point. A
pH above 6.5 to 7 should be avoided during the preparation because
the higher initial pH's tend to result in the formation of alumina
hydrates such as bayerite, nordstrandite and gibbsite. After the
desired amount of aluminum chloride has been added, the ammonium
hydroxide addition is continued until a pH of 8 to 10, preferably 9
to 10, is achieved to complete the crystallization more
rapidly.
Further, it is important but not critical that the precipitated
alumina dihydrate be dried rapidly since the precipitate as formed
is unstable and tends to transform into other alumina hydrates
having a higher or lower water of hydration content. One with
ordinary skill in the art will soon be able to determine through a
few simple drying experiments the amount of time he can afford to
expend between precipitation and drying in order to retain the
X-ray diffraction pattern characteristics for the precursor alumina
as defined above. The drying, of course, tends to "set" the X-ray
diffraction pattern characteristics. Normally, drying occurs at
temperatures from 250.degree. to 500.degree. F. (121.degree. to
260.degree. C.) for times of from 1 to 20 hours.
In the preparation of the alumina hydrate containing from 1.2 to
2.6 moles of water of hydration, any aluminum salt may be employed.
For instance, aluminum nitrate, chloride, acetate, formate,
fluoride, sulfate and other salts of aluminum may be used. Also, a
variety of bases such as sodium hydroxide, ammonium hydroxide,
potassium hydroxide, etc., may be employed to precipitate the
aluminum hydrate. It is preferred, however, to employ salts of
aluminum and bases which do not give reaction by-products or salts
which are difficult to separate from the desired alumina hydrates.
For instance, if aluminum sulfate and/or sodium hydroxide are
employed or even if aluminum sulfate or ammonium hydroxide are
employed, sulfate salts are formed which are difficult to remove by
water washing. On the other hand, if aluminum nitrate, aluminum
chloride or an aluminum salt of an organic acid is used and a base,
such as ammonium hydroxide, is employed, the salts which are formed
are readily soluble in water and can easily be removed from the
aluminum hydrate by water washing and/or calcination. Regardless of
the specific aluminum salt and base that are used, the final
product should be substantially free of such salts.
The carrier employed in the process of this invention can be in the
form of irregular particles obtained by crushing or grinding or it
can be in the form of more regular shapes such as cylindrical
extrudates or spherical beads. In the preparation of beads such as
for use in fluidized bed operations or in the preparation of
extrudates of enhanced strength, the use of binder materials such
as silica, for example in the form of silicic acid or synthetic and
natural clays, can be employed. Such binders are present in an
amount from about 8 to 10% by weight up to about 30% by weight
based upon the total.
The alumina carriers described above are preferably calcined by
heating in air for time periods from 1 to 20 hours before the
addition of the metalliferous hydrogenation components as described
earlier. Such calcining, however, prior to the addition of metals,
is not critical but is preferred. Added drying and calcining
occurs, of course, after metals addition.
The invention will be further described with reference to the
following experimental work.
EXAMPLE 1
A solution of an aluminum salt was prepared by dissolving 483 grams
of AlCl.sub.3.6H.sub.2 O in 4 liters of distilled water. A separate
ammonium hydroxide solution was prepared by dissolving 1 liter of
concentrated ammonium hydroxide in 2 liters of distilled water. A
stirring medium was provided by adding 1 liter of distilled water
to a mixing vessel, and a motor-driven stirrer and pH electrodes
were positioned in this water. The aluminum salt solution and the
ammonium hydroxide solution were added separately, in thin streams,
to the mixing zone, accompanied by vigorous stirring. The relative
rate of addition of these two solutions were adjusted to maintain a
constant pH = 5.5 in the mixing zone where a precipitate was formed
by the reaction of the two solutions. After all of the aluminum
salt solution was added, the addition of the ammonium hydroxide
solution was stopped, and stirring was continued for five minutes.
Addition of the ammonium hydroxide solution was then continued to
raise the pH of the final mixture to 10.0. The precipitate was left
to age in the mother liquor for one hour, after which the
precipitate was recovered by filtration and washed on the filter
with 4 liters of distilled water, the pH of which was adjusted to
10.0 by the addition of ammonium hydroxide. The washed filtercake
was dried at 120.degree. C., and the X-ray diffraction pattern of
this oven-dried product is shown in FIG. 1.
Analysis of the precursor alumina did not reveal any trihydrate of
alumina, despite the aging of the precursor. The (020) line width
of the X-ray diffraction pattern at about 14.degree. (2 .theta.) at
three-fourths maximum intensity and the intensity ratio for the
precursor alumina before calcining are given in Table I below.
FIG. 1 is the X-ray diffraction pattern for the oven-dried
precursor of aluminum made in accordance with this Example 1.
EXAMPLE 2
The preparation of Example 1 was repeated except the aluminum
chloride solution contained 1000 grams of AlCl.sub.3. 6H.sub.2 O in
10 liters of distilled water. Also, the filtercake was washed with
10 liters of water, the pH of which was adjusted to 10 with
NH.sub.4 OH.
Analysis of the precursor alumina showed the presence of about 2%
by weight of the trihydrate of alumina. It was determined by X-ray
diffraction that about 98% of the alumina hydrate was the dihydrate
having from 1.2 to 2.6 moles of water per mole of alumina. The
(020) line width of the X-ray diffraction pattern at about
14.degree. (2 .theta.) at three-fourths maximum intensity and the
intensity ratio for the precursor alumina before calcining are
given in Table I below.
EXAMPLE 3
Example 2 was repeated. Analysis of the precursor alumina did not
reveal the presence of any trihydrate of alumina despite the aging
of the precursor alumina. The (020) line width of the X-ray
diffraction pattern at about 14.degree. (2 .theta.) at
three-fourths maximum intensity and the intensity ratio for the
precursor alumina before calcining are given in Table I below.
EXAMPLE 4
The preparation of Example 1 was repeated except the precursor
alumina was not aged for one hour before drying. No trihydrate of
alumina was found by analysis. The (020) line width of the X-ray
diffraction pattern at about 14.degree. (2 .theta.) at
three-fourths maximum intensity and the intensity ratio for the
precursor alumina before calcining are given in Table I below.
EXAMPLE 5
The preparation of Example 4 was repeated except the pH during
precipitation of the alumina was maintained at about 4.5 rather
than 5.5, and the final pH was about 9.5 rather than 10. Again, no
trihydrate of alumina was found in the precursor. The (020) line
width of the X-ray diffraction pattern at about 14.degree. (2
.theta.) at three-fourths maximum intensity and the intensity ratio
for the precursor alumina before calcining are given in Table I
below.
EXAMPLE 6
The preparation of Example 4 was repeated except the pH during
precipitation of the alumina was maintained at about 6.2 rather
than 5.5. Again, no trihydrate of alumina was found in the
precursor. The (020) line width of the X-ray diffraction pattern at
about 14.degree. (2 .theta.) at three-fourths maximum intensity and
the intensity ratio for the precursor alumina before calcining are
given in Table I below.
EXAMPLE 7
A first solution was made by dissolving 2000 grams of AlCl.sub.3
.6H.sub.2 O and 8000 grams of NH.sub.4 Cl in 20 liters of water (ph
= 2). A second solution was formed by admixing 3000 cc of water and
3000 cc of ammonium hydroxide. The second solution was added slowly
with vigorous stirring to solution 1. The slurry gelled after 3500
cc of solution 2 had been added. The gel was broken by vigorous
stirring by hand, and the addition of the ammonium hydroxide
solution (No. 2) was continued until a pH of 8.0 was reached. This
required the addition of substantially all of the ammonium
hydroxide solution, and stirring was continued for an additional 30
minutes. The slurry was filtered; washed briefly on the filter; and
oven dried. The X-ray diffraction pattern of the oven-dried
material is shown on FIG. 2. The (020) line width of the X-ray
diffraction pattern at about 14.degree. (2 .theta.) at
three-fourths maximum intensity and the intensity ratio for the
precursor alumina before calcining are given in Table 1 below.
TABLE 1 ______________________________________ CHARACTERISTICS OF
(020) X-RAY DIFFRACTION LINE OF ALUMINA HYDRATE PRECURSORS Line
Width at Intensity Ratio Ex. about 14.degree. (2 .theta.) Peak/min.
at No. at 3/4 max. intensity about 10.degree. (2 .theta.)
______________________________________ 1 3.0.degree. 2.0 2
4.3.degree. 1.6 3 3.6.degree. 1.8 4 4.4.degree. 1.6 5 2.3.degree.
2.8 6 2.7.degree. 1.8 7 1.6.degree. 10
______________________________________
Referring to Table 1, it can be observed that the line widths of
all of the precursor aluminas from Examples 1 through 7 were
relatively wide, the widest being 4.4.degree.. The intensity ratios
of the aluminas of Examples 1 through 6 are relatively small (less
than 3), whereas the intensity ratio from the alumina from Example
7 (the prior art) was relatively high at 10.
EXAMPLE 8
A solution of an aluminum salt was prepared by dissolving 9460
grams of AlCl.sub.3.6H.sub.2 O in 40 liters of distilled water. To
this solution was added 1000 grams of glacial acetic acid to
provide a final solution having a pH of 1.49 at 24.degree. C. A
separate dilute ammonium hydroxide (8% NH.sub.3) solution was
prepared by dissolving 10 liters of concentrated ammonium hydroxide
in 25 liters of distilled water. The dilute ammonium hydroxide
solution was added to the aqueous aluminum chloride and acetic acid
solution with stirring to form a gel at a pH in the range from 4 to
5 at 25.degree. C. Addition of the ammonium hydroxide solution was
then continued to raise the pH of the final mixture to 8.
Transformation to alumina trihydrate, as described above, was
effected by stirring this material from 10 to 15 minutes after the
pH of 8 was reached. Further transformation was effected by placing
the material on a filter and washing with a dilute ammonium
hydroxide solution (0.028% NH.sub.3) until the conductivity of the
filtrate reached 1000 ppm.
The filtercake consisted of two discrete phases or layers at the
end of the washing operation. The top layer represented about 10 to
15% by volume of the total filtercake and consisted mainly of
bayerite and was white and gritty. The lower layer was gelatinous,
substantially uniform and consisted of about 10 to 15% bayerite
dispersed in alumina gel. The top layer was discarded and the lower
layer was oven dried at 250.degree. F. (121.degree. C.) for 16
hours and thereafter sized to 14.times.30 mesh granules and
calcined at 900.degree. F. (482.degree. C.) for 16 hours. FIG. 5 is
the X-ray diffraction pattern for the oven-dried precursor alumina
made in accordance with this Example 8.
There is no line width or intensity ratio for the material prepared
in accordance with this Example, and thus although the material is
about 85% to 95% alumina dihydrate, the X-ray diffraction pattern
characteristics are considerably different in the 8.degree. to
16.degree. (2 .theta.) region.
EXAMPLE 9
A first solution of 5000 grams of AlCl.sub.3.6H.sub.2 O in 40
liters of water was prepared. A second solution was made by
dissolving 5 parts of ammonium hydroxide with 12 parts of water.
Approximately 10 liters of solution 1 were added to a mixing vessel
containing 8 liters of water, and the pH was found to be 3.1. The
ammonium hydroxide (second solution) was slowly added with vigorous
stirring until a pH of 6.5 was achieved. A thick gel formed at an
intermediate pH, which had to be broken with vigorous
hand-stirring. The remainders of solutions 1 and 2 were then added
simultaneously, at a slow rate in such a ratio that the pH of 6.5
was maintained. When all of solution 1 was added, stirring was
continued together with the addition of the ammonium hydroxide
solution until a pH of 9.0 was reached.
The slurry was filtered immediately and washed with 50 liters of
water adjusted to a pH of 9.0 with ammonium hydroxide. The total
elapsed time from the completion of the precipitation until the
filtercake was removed from the filter after washing was 5 3/4
hours. The filtercake was oven dried at 125.degree. C., and an
X-ray diffraction pattern was obtained and is shown on FIG. 3. Like
Example 8, the alumina from Example 9 showed no (020) line width or
intensity ratio in the region of 14.degree. (2 .theta.).
EXAMPLE 10
The preparation of Example 9 was repeated except the final pH
during precipitation was 8.0. The wash water had a pH of 8.0, and
the total elapsed time from the beginning of precipitation until
the filtercake was removed from the filter was 4 hours and 5
minutes. The X-ray diffraction pattern for the oven-dried material
is shown on FIG. 4, and again there is no (020) line width or
intensity ratio in the 8.degree. to 16.degree. (2 .theta.)
region.
EXAMPLE 11
The catalyst for this Example is a commercially prepared catalyst
containing 0.5 weight percent nickel, 1.0 weight percent cobalt,
and 8 weight percent molybdenum on a gamma-alumina support.
Each of the dried and calcined alumina composites shown in Examples
1 through 9 above was impregnated with nickel, cobalt and
molybdenum solutions, after which each catalyst was again oven
dried at 250.degree. F. (121.degree. C.) for 16 hours and calcined
at 900.degree. F. (482.degree. C.) for 16 hours. Each of the final
catalysts contained 0.5% by weight nickel, 1% by weight cobalt, and
8% by weight molybdenum.
Each of the catalysts made from the aluminas of Examples 1 through
9 and the catalyst of Example 11 above were evaluated for the
desulfurization of a reduced Kuwait crude whose properties are
shown on Table 2 below.
TABLE 2 ______________________________________ Gravity,
.degree.API, D287 16.8 Sulfur, wt % 3.76 Nickel, ppm 14 Vanadium,
ppm 47 Carbon Residue, Ramsbottoms, wt % 8.34 Pentane Insol, D893,
wt % 6.90 Distillation: % Condensation at 760 mm 5 611.degree. F.
(322.degree. C.) 10 667.degree. F. (353.degree. C.) 20 740.degree.
F. (393.degree. C.) 50 929.degree. F. (498.degree. C.) 70
1014.degree. F. (545.degree. C.)
______________________________________
The test conditions were: 1000 psig (6.89 MPa); 700.degree. F.
(371.degree. C.); 1 LHSV; with the addition of 5000 SCF of hydrogen
per barrel of feedstock. The feedstock was passed downflow through
a bed of the catalyst, and the products were recovered and analyzed
for sulfur content by standard combustion technique (Leco
method).
The product sulfur with time for each of the catalysts shown on
Examples 1-9 and 11 above is summarized in Table 3 below, in
addition to the percent desulfurization obtained after 40 hours
on-stream.
TABLE 3 ______________________________________ DESULFURIZATION OF
REDUCED KUWAIT CRUDE Wt % Catalyst Wt % Sulfur in Liquid
Desulfurization from Product at: After 40 hours Ex. No. 10 hrs. 20
hrs. 40 hrs. On-Stream ______________________________________ 1
0.92 0.96 0.98 73.9 2 0.89 0.91 0.92 75.5 3 0.88 0.89 0.90 76.1 4
1.06 1.075 1.095 70.9 5 1.035 1.07 1.105 70.6 6 1.07 1.13 1.16 69.1
7 2.08 2.18 2.25 40.2 8 1.14 1.18 1.22 67.6 9 1.40 1.41 1.45 61.4
10 -- -- -- -- 11 1.04 1.20 1.35 64.1
______________________________________
The results in Table 3 are also shown graphically on FIG. 6.
Referring to Table 3 and FIG. 6, it can readily be seen that the
catalysts prepared using the aluminas of this invention as the
catalyst support (Exs. 1-6 above) resulted in a much lower weight
percent sulfur in the liquid product (a better percent
desulfurization) than catalysts prepared using as a support the
aluminas of the prior art (Exs. 7,8,9 and 11) In addition, the
commercial catalyst of Ex. 11 has poorer aging characteristics than
the catalysts using the aluminas of the present invention (Exs.
1-6).
Resort may be had to such variations and modifications as fall
within the spirit of the invention and the scope of the appended
claims.
* * * * *